As storage devices mainly composed of a positive electrode, a negative electrode and a non-aqueous electrolyte, various constructions have been proposed, and they have been practically used for electric sources of mobile apparatuses, storage systems for regeneration, backup electric sources of personal computers, etc. Among them, electric double-layer capacitors in which graphite is used as positive electrode material and a carbonaceous material is used as negative electrode material are superior, in capacitance and dielectric strength, to conventional storage devices using activated carbon for electrode (see Patent Document 1).    Patent Document 1: JP-A-2005-294780